<!--
 * @Description: 事件
 * @Author: charles
 * @Date: 2021-11-09 09:22:10
 * @LastEditors: charles
 * @LastEditTime: 2021-11-09 10:29:04
-->
<!DOCTYPE html>
<html lang="en">
<head>
  <meta charset="UTF-8">
  <meta http-equiv="X-UA-Compatible" content="IE=edge">
  <meta name="viewport" content="width=device-width, initial-scale=1.0">
  <title>函数组件</title>
  <script src="https://cdn.bootcdn.net/ajax/libs/react/17.0.2/umd/react.development.min.js"></script>
  <script src="https://cdn.bootcdn.net/ajax/libs/react-dom/17.0.2/umd/react-dom.development.min.js"></script>
  <script src="https://cdn.bootcss.com/babel-standalone/6.26.0/babel.min.js"></script>
</head>
<body>
  <div id="app"></div>

  <script type="text/babel">
    const useState = React.useState;
    const useEffect = React.useEffect;
    
    function App(props){
      let [num,setNum] = useState(1);

      const changeNum = ()=>{
        setNum(++num)
      }  
    

      useEffect(()=>{
        // 考虑如何在componentDidMount调用
        changeNum();

      },['num']);

      console.log('render....');
      return (
        <div>
          <h1>函数组件</h1>  
          <div>状态num { num }</div>
        </div>
      )
    }
    ReactDOM.render(<App/>,document.getElementById('app'))
  </script>
</body>
</html>